The present invention relates to a decanter centrifuge comprising a motor-driven rotary drum, a conveyor screw located within said drum and rotatable relative thereto for conveying solid material separated from a raw material supplied to the drum, a mechanical gearing connecting said drum and said conveyor screw, said gearing including a housing rigidly connected to said drum and an input shaft the rpm. of which determines the rpm. of the screw relative to the drum.
By adjusting or varying the rpm. of the input shaft of the gearing it is possible to change the conveying rate of the screw and thus adapt that rate to the prevailing operational conditions, e.g. in order to obtain a minimum of solids in the liquid phase discharged and/or a maximum dewatering of the solids, or in order to prevent overloading of the centrifuge in case the content of solids in the raw material is particularly high.